Abstract
Purpose :
Quantification of episcleral venous outflow is a potential method to determine the efficacy of glaucoma interventions such as medical therapy and minimally invasive glaucoma surgeries. Prior work has demonstrated that fluorescently labeled erythrocytes can quantify episcleral flow. The purpose of this study is to determine the reproducibility of a noninvasive approach to quantifying episcleral flow (EF) using laser speckle contrast imaging (LSCI) in a rabbit model at varying intraocular pressures (IOP).
Methods :
We conducted 8 imaging sessions on different days on 5 eyes of 3 male New Zealand white rabbits. Four 3-second LSCI videos were captured to provide baseline EF data. Using a validated syringe pump model, the anterior chamber was cannulated, and the IOP was raised from 20 mmHg to 60 mmHg in increments of 10 mmHg. Indocyanine green (ICG) was also injected intravenously to visualize the episcleral veins. LSCI videos were captured at each fixed IOP. The LSCI data was processed by averaging blood flow velocity indices (BFVi) in two blood vessel segments per video and mean, peak, and dip BFVi values were extracted from the pulsatile waveforms. The coefficients of variation (CVs) for each variable were determined to quantify the intrasession and intersession variability.
Results :
The average baseline EF across the 8 imaging sessions for the 5 eyes was 6.0±2.0 arbitrary units (AU). The intrasession variability ranged from 1.4±0.3% to 2.4±0.7%. The average CVs for IOPs of 20 mmHg - 60 mmHg within each session ranged from 1.2±0.2% to 1.8±0.4%. Intersession variability ranged from 2.4±0.5% to 5.19±0.04%. Intersession variability for each IOP ranged from 1.9±0.1% - 6.9±0.1%. Table 1 depicts the CVs for each rabbit and at each IOP.
Conclusions :
Across the 8 imaging sessions of the 5 eyes, we observed highly repeatable values of episcleral flow in a rabbit model both at baseline and at elevated intraocular pressures. This model can be used to test the effect of medications and surgical interventions on episcleral blood flow.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.